Idunn Mons on Venus with recent emissivity data from the Venus Express overlaid on the topography, suggesting recent lava flows.

NASA released images today that suggest that the surface of Venus has experienced some relatively recent volcanic events (geologically speaking). By examining the surface in infrared, the Venus Express, launched by the European Space Agency (ESA) has found that three spots on the surface exhibit signs of recent volcanism. The long-and-short of the research lead by Dr. Sue Smrekar of JPL is that a number of Venutian lava flows (shown above on Idunn Mons) show less evidence of weathering at the surface of Venus, based on their composition – suggesting that these flows may be geologically young. In the press release, the estimate for the age of the flows is as “recent as 2,500,000 years”, which to many people seems old, but geologically, those are young flows, especially on a planet where the current level of geologic activity is unclear. However, the JPL team goes on to suggest that these flows could be even younger than 2.5 million years and might suggest current activity on the second planet. The surface of Venus is almost entirely relatively free of impact crater, which suggests to some that the surface must be young, but as of yet, we have no direct evidence of current evidence of eruptions. All the activity on Venus would appear to be basaltic based on data collected by Russian Venera landers, although some features look like rhyolite domes as well (their origin is unknown). However, there has been some tantalizing hints of a potentially active neighbor.

@2 Bruce,
I haven’t kept up with the developments on thoughts about Venus, but I do know that a mantle plume scenario was very popular. Venus does have features that resemble large shield volcanoes and domes, and their sizes suggest that they remain relatively fixed in place.
@3 Alex,
Plate tectonics simply means that most crustal features (rift valleys, mountains, continents, basins, and volcanoes) are built (tectonics) due to the lateral movements and interactions of plates. On Earth the presence of water plays a big role in PT. Venus is bone dry so if there is something similar it must operate differently.

Erik, maybe you could toss a link to basic Venusian geology and volcanics. I know I’ve seen one somewhere, but have no idea where.

Since all the water has been outgassed and dissociated by UV light, the crust is bone-dry and too rigid to permit plate tectonics. I assume the current volcanism is a matter of mantle plumes. In the absence of plate tectonics and associated cooling as the crust overturns, the vertical temperature gradient gets so steep that the system gets unstable. Eventually, after about half a billion years, Venus gets resurfaced by massive volcanism.
In the absence of plate tectonics and continents, the surface of Venus does not depart much from the average surface level. Also, tidal effects have practically eliminated the axial rotation. If a planet can be called “depressing” Venus is it.

Nice post! One small correction: Venus does have impact craters, it’s not like Titan or Io where the surface must be very young. Craters indicate that most of the surface is less than a billion years old (600 million years is what I remember for a common estimate). Venus just does not have any small craters because its thick atmosphere is stopping small asteroids, and without small craters you can’t date young surfaces.

I don’t know much about Venus, but I know a lot about Mars. Mantle convection still occurs in terrestrial planets without plate tectonics. Whether or not convection occurs is a function on mantle thickness, viscosity, and temperature difference. The Tharsis Bulge must be buoyed by mantle upwelling because it is too high to be held up by lthospheric thickening alone. Where mantle moves up, melting occurs. But mantle upwelling does not necessary mean PLUME. The youngest volcanic rocks on Mars are very low-K (as are the shergottitic meteorites), suggesting that they originate from a depleted mantle, not an enriched plume. My point is that a single lithospheric plate does not rule out mantle melting by means other than plumes or impacts. I hope that makes sense!

A geologist on the Russian TV News in English (Channel 85 in the UK)has announced (5am BST) that if Katla blows it could `destroy half of Iceland’. That is open to more than one scientific interpretation so let’s hope that something got lost in translation or it’s simple exaggeration – not that the Russians know more about the magma chamber than the rest of the world does…

Meanwhile, the health authorities here are very laid back about the potential hazards of the ash, so thanks for the link to the USGS site.